1. Field of the Invention
The present invention generally relates to enhancements in devices for filtering and separating liquids. More particularly, the present invention relates to fuel filters for removing foreign particles and separating water from fuel of a fuel supply system associated with an internal combustion engine. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Related Art
Diesel fuel supplies frequently contain significant quantities of abrasive particles and water which present the potential for permanent damage to the components of the fuel injection pump, the fuel delivery system and other components of the engine. Consequently, an effective fuel filter assembly for removing such particles and water from the fuel is a practical necessity and is conventionally incorporated into the fuel supply system of a diesel engine. A multitude of conventional fuel filter assemblies employ a disposable filter cartridge which is replaced at pre-established intervals of filter usage. Such filter cartridges typically perform the dual function of removing particulate material from the diesel fuel and separating water from the fuel.
The fuel filter assemblies to which the present invention relates include a replaceable filter cartridge and a header with a base which accepts the disposable filter cartridge. The filter cartridge has a housing which defines an opening at one end thereof to provide fuel communication between the fuel delivery system and a filter element disposed within the cartridge housing. A sealing grommet is disposed at the opening to provide a fluid-tight seal. The fuel filter cartridges may house a single stage filter or a dual stage filter and may assume a wide variety of shapes and configurations.
Conventional headers used with such fuel filter assemblies include a fuel entry port which is in fluid communication with a central axial fuel conduit for transporting fuel to be filtered into the filter cartridge. Additionally, a fuel exit port of the header is fluidly connected to a coaxial fuel conduit disposed about the central fuel conduit and cooperating therewith to define a fuel exit passage therebetween. Thus, fuel to be filtered conventionally enters the fuel cartridge via the central fuel conduit, is filtered therein and then exits the filter cartridge via the fuel exit passage which surrounds the central fuel conduit. Recent developments have included reversing the operation of the central fuel conduit and the fuel exit passage.
In such conventional fuel filter assemblies, water separation has often been achieved by employing a filter element which comprises a continuous fan-shaped, pleated configuration symmetrically disposed within the filter cartridge and possessing water coalescing properties. In such a filter element, fuel is allowed to pass therethrough, but water is not. Thus, water droplets form at the outside of the filter element and fall to the bottom of the filter cartridge. A drain cock is often mounted at the bottom of the filter cartridge for draining the collected water from the filter. Other filter cartridges employ a filter sock to perform the particulate matter removing and water separating functions. In such sock filters, water is removed from the fuel and coalesces at the sock filter, but the water is also allowed to pass through the sock filter in the form of water droplets. Such designs rely on the force of gravity to pull the water droplets to the bottom of the filter and away from the fuel stream so that the water does not, once again, become swept away with the fuel stream. Naturally, such designs cannot guarantee that the water droplets removed from the fuel will not reenter the fuel stream thereby defeating the purpose of water separation in the first place. In fact, this deficiency may be particularly acute in filter cartridges employing sock filters because the water is not entirely prevented from passing through the sock filter, but is merely forced to coalesce and pass therethrough at a different rate than the fuel.
Accordingly, there is a need in the art for improved fuel filter cartridges and methods therefor which more effectively separate water from the fuel stream as the fuel passes through the filter cartridge.